1. Field of the Invention
The present invention relates to an image forming apparatus and method, and more particularly, to image forming technology suitable for an inkjet recording apparatus which forms images on a recording medium by ejecting liquid droplets from nozzles.
2. Description of the Related Art
An inkjet type of image forming apparatus records text and images (hereinafter, generally called an “image”) by means of dots of ink deposited on a recording medium such as a recording paper, by ejecting ink droplets from nozzles of a print head.
Japanese Patent Application Publication No. 2004-90596 discloses an image forming apparatus which comprises a device which applies a liquid for hydrophilizing the recording surface of the medium, a device which applies a liquid for raising the viscosity of the ink onto the recording surface which has been hydrophilized, and a device for an image formed by ejecting ink after applying the viscosity-raising liquid. This apparatus is proposed with a view to forming a desirable image without the occurrence of defects, such as beading (i.e., ink repulsion and combination defects) and bleeding (i.e., color mixing defects), on various types of non-absorbent recording surface which do not have ink-absorbing properties, a typical embodiment of which is an OHP sheet.
In respect of image forming methods using ink containing a coloring agent (coloring material) such as dye or pigment, and a reactive liquid (treatment liquid) containing a compositional material having the property of reacting with compositional material of the ink, various methods have been proposed (for example, see Japanese Patent Application Publication Nos. 2001-179959, 6-99576, 5-202328, 9-286940 and 11-348255).
Japanese Patent Application Publication No. 2001-179959 discloses an image apparatus in which a solvent absorbing body having a surface with good separating properties with respect to the ink coloring material is made to contact ink on a medium, thereby absorbing the solvent (the solvent of the ink remaining on the recording medium after printing, and especially the liquid solvent (generally, water) which is the main component of the ink). This apparatus prevents the image on one sheet from transferring another sheet when a plurality of sheets of recording medium are printed. Furthermore, Japanese Patent Application Publication No. 2001-179959 also discloses a composition in which, the coloring material in the ink is converted into particles by using an aggregation promoter which causes the coloring material (dye or pigment) in the ink to aggregate and deposit, and the solvent absorbing body is placed in contact with the ink in a state where the coloring material and the liquid solvent have separated into different phases, thereby absorbing the solvent only.
Japanese Patent Application Publication No. 6-99576 discloses an inkjet recording method in which a solution containing a polymer having opposite polarity to that of the polymer contained in the recording liquid (ink) is sprayed onto the recording medium before recording, and an image is then recorded by ejecting the recording liquid onto the portion where liquid droplets of the solution have been applied. This method is proposed with a view to ensuring good printing quality on various different types of recording paper, as well as obtaining a recorded image having excellent durability, such as scratch resistance, water resistance, light resistance, and the like.
Moreover, technologies for causing the coloring material to aggregate by using a multivalent metallic salt solution are known (see Japanese Patent Application Publication Nos. 5-202328, 9-286940, and 11-348255). Japanese Patent Application Publication No. 11-348255, for example, discloses a method that obtains a good image by changing the amount of reactive liquid according to the droplet ejection sequence of the ink liquid and the reactive liquid.
Although Japanese Patent Application Publication No. 2004-90596 proposes the use of two types of treatment liquid in order to prevent beading and bleeding, it does not provide any disclosure regarding the processing (removal) of the solvent remaining on the media. Japanese Patent Application Publication No. 2001-179959, on the other hand, describes technology for absorbing and removing solvent from the media; however, it does not mention technology for avoiding landing interference.
Landing interference is a phenomenon that occurs when ink droplets combine on the surface of the recording medium immediately after landing, thus deforming the original independent shapes of the droplets and disrupting the shapes of the dots. Concerning inks of different colors, the problem of color mixing can occur when the inks of different colors interfere with each other in sections where the dots were not supposed to have overlapped. Even in the case of ink of the same color, the prescribed dot shape (for example, an ideal circular shape) is lost, and hence the image is degraded. Especially, the landing interference is important in cases where droplets are ejected to form mutually adjacent dots at short time intervals (at high speed).
Japanese Patent Application Publication Nos. 6-99576, 5-202328, 9-286940, and 11-348255 provide disclosures relating to the composition of the ink liquid and the treatment liquid (reactive liquid). However, they do not discuss the avoidance of landing interference, the separation of the coloring material and solvent, and the processing of the solvent once separated.